Glossary of Heating, Ventilation and Air Conditioning Terms

A calculation of the total glass load to see if any hourly total exceeds the 12 hr average by more than 20 or 30%

AFUE

Annual Fuel Utilization Efficiency. AFUE is a rating that reflects how efficiently a gas furnace converts fuel to energy. An AFUE of 90 means that approximately 90 percent of the fuel is utilized to provide warmth to your home, while the remaining 10 percent escapes as exhaust.

Air Balancing

Adjusting an air conditioning system so that the right amount of air is delivered to the right places in your home in order to achieve the proper heating and cooling effect.

Air Cleaner

A device that removes allergens, pollutants and other undesirable particles from air that is heated or cooled.

Air Conditioner

Equipment htat conditions air by cleaning, cooling,heating, humidifying or dehumidifying it. A term often applied to comfort cooling equipment.

Air Filter

A device for removing particulate material from the air stream. The higher the MERV rating the better the filter.

Air Handler
The portion of your air conditioner or heating system that forces air through your home's ductwork.

ARI

Air Conditioning and Refrigeration Institute, a non-profit, voluntary organization composed of heating, air conditioning and refrigeration manufacturers. ARI publishes standards for testing and rating heat pumps and air conditioners.

Aspiration

Using a partial vacuum to draw up gas. Air that is discharged at a high velocity from our outlets creates a vacuum, and the air is then pulled into this vacuum creating a blend of conditioned air.

Balance Point

An outdoor temperature, usually between 30° F and 45° F, at which a heat pump's output exactly equals the heating needs of the home. Below the balance point, supplementary electric resistance heat is needed to maintain indoor comfort.

Brazing

A process that is used to bond similar or dissimilar materials by melting a filler metal or alloy placed between the components being joined. Brazes are filler metals or alloys that melt at temperatures above 450°C.

Breaker

A heat activated electrical device used to open an electrical circuit to protect it from excessive current flow.

BTU
A British Thermal Unit (BTU) is the unit of heat required to raise 1 pound of water by 1 degree Fahrenheit. Used for both heating and cooling, BTU is a measure of the heat given off when fuel is combusted. Or for cooling, it's a measure of heat extracted from your home. (One BTU is approximately equal to the heat given off by a wooden kitchen match.)

BTUH
British Thermal Units per Hour. A British Thermal Unit (BTU) is the unit of heat required to raise 1 pound of water by 1 degree Fahrenheit.

Capacity

The output or producing capability of a piece of cooling or heating equipment. Cooling and heating capcity are normally referred to in BTU'S.

Capillary Tube

A refrigerant control consisting of a small diameter tube which controls flow by restriction. They are carefully sized by inside diameter and length for each particular application.

Central Air Conditioner

Central air conditioning systemshave essentially two parts: an evaporator that removes unwanted heat from the air and transfers it to a refrigerant; and an condenser that removes unwanted heat from the refrigerant and transfers that heat outdoors. The primary component of a condenser is typically the condenser coil, through which the refrigerant flows.

CFM
Stands for Cubic Feet per Minute. A measurement of airflow that indicates how many cubic feet of air pass by a stationary point in one minute. The higher the number, the more air is being forced through the system.

Circuit Breaker

A device that opens an electric circuit when an overload occurs.

CLF

Cooling Load Factor

Compressor

The compressor squeezes the molecules of the refrigerant gas together, increasing the pressure and temperature of the refrigerant.

Condensate

The moisture collected on an evaporator coil.

Condenser Coil

Part of the outdoor portion of a split-system air conditioner or heat pump. By converting refrigerant that is in a gas form back to a liquid, the coil sends heat carried by the refrigerant to the outside. Also referred to as an Outdoor Coil.

Condensing Unit

The outdoor component of a cooling system. It includess a compressor and condensing coil designed to give off heat. It also changes the vapor gas mixture back to a liquid for return to the system.

Damper
A type of "valve" used in duct work that opens or closes to control airflow. Used in zoning to control the amount of warm or cool air entering certain areas of your home.

Dehumidification

The reduction of water vaport by cooling the air below the dew point,as well as the removal of water vapor from the air by chemical means, refrigeration, etc.

Delta T

A term indicating a temperature relationship between two temperatures or temperature variation between two points.

Drip Pan

A Pan shaped to collect moisture condensing on an evaportator coil in an air conditioning system.

Dry Bulb Temperature

Temperature read with an ordinary thermometer.

Ductwork

Hollow pipes used to transfer air from the Air Handler to the air vents throughout your home. Ductwork is one of the most important components of a home heating and cooling system.

EER
Energy Efficiency Ratings (EER) measure the efficiency with which a product uses energy to function. It is calcuated by dividing a product's BTU output by its wattage.

Electric Heat

The process of converting electrical energy, using resistance, into heat.

Electronic Air Cleaner

An electronic device that filters out large particles and contaminants in indoor air. It then electronically pulls out tiny particles that have been magnetized, such as viruses and bacteria, drawing them to a collector plate.

Evaporator Coil

Part of a split-system air conditioner or heat pump located indoors. The evaporator coil cools and dehumidifies the air by converting liquid refrigerant into a gas, which absorbs the heat from the air. The warmed refrigerant is then carried through a tube to the outdoor unit (condenser coil). Also referred to as an indoor coil.

Fan Coil Unit

The fan distributes air through the plenum; the coils cool (or heat and cool) the air, depending on individual needs and system configuration. Connects to external condenser for cooling; SpacePak is compatible with most condenser brands.

Flexible Supply Tubing

These flexible, narrow, tubular ducts enable SpacePak to bring central air throughout the house within the normal space between walls, ceilings, or floors: no extensive renovation work. The number of ducts would be based on the size of the fan coil unit.

Geothermal Heat Pump

A heat pump that uses the earth or water in the earth for its heat sources and sinks.

Heat

Form of energy which acts on substances to raise their temperature; energy associated with random motion of molecules

Heat Gain

The transfer of heat from outside to inside by means of conduction, convection and radiation through all surfaces of a house.

Heat Pump

A product that works just like an air conditioner in cooling mode however, in heating mode, the refrigerant flow is reversed and heat is extrated from the outside air too heat your home.

Humidifier

A device that adds moisture to dry indoor air during wintertime and in hot dry climates.

HVAC
Heating, Ventilation and Air Conditioning (HVAC).

IAQ
Indoor Air Quality (IAQ) refers to the cleanliness and health of the air in a home.

Indoor/Outdoor System

Refers to a comfort system consisting of components in two locations. Common examples include an outside unit, such as an condensing unit, and an indoor unit such as an fan coil unit.

Infiltration

Air that leaks into a structure through cracks, windows, doors or other openings due to less pressure inside the structure than outside the structure.

Kwik Connects

A no-tools-required system that quickly and easily joins the flexible ducts to sound attenuators and the plenum. Kwik Connects virtually eliminate leakage, improving efficiency, and greatly reduce install time.

Latent Heat

Heat, that when added or removed, causes a change in state - but no change in temperature.

Liquid Line

A tube used to convey the liquid refrigerant from the condenser outlet to the refrigerant control device of the evaporator.

Load Estimate

A series of studies performed to determine the heating or cooling requirements of your home. An energy load analysis uses information such as the square footage of your home, window and door areas, insulation quality and local climate to determine the heating and cooling capacity needed by your furnace, heat pump or air conditioner.

Manometer

An instrument used for measuring the pressure of liquids and gases.

Matched System

An air conditioner or heat pump system composed of equipment that has been certified by ARI to work together to deliver the specified heating and cooling capacity at the stated efficiency rating.

Nitrogen

An inert gas often used to 'sweep' a refrigeration system to help ensure that all refrigerant and contaminants have been removed.

Open -loop heat pump

Heat pump system that uses water in the earth as the heat transfer medium and then expels the water back to the earth in some manner.

Outdoor Coil/Condensing unit

The portion of a refrigeration system where the compression and condensation of refrigerant is accomplished. Sometimes referred to as the 'high side'.

Outlet

How the conditioned air enters the living space. These 5" diameter outlets (the size of a music CD; much smaller than conventional register grilles) can be placed in the ceiling, wall, or floor.

Plenum

Carries air to the different ducts which distribute it throughout the house. The plenum fits within the attic, basement, or crawl space where the fan coil unit is installed.

Programmable Thermostat

A type of thermostat that allows the user to program into the devices' memory a pre-set schedule of times (when certain temperatures occur) to turn on HVAC equipment

PurePak Air Cleaner

A patented design that replaces the standard return air box. While 4–6" pleated filters are not effective at removing contaminants smaller than three microns (such as bacteria, auto exhaust, cooking smoke, dust, or paint pigments), PurePak captures contaminants as small as 0.3 microns with 97% effectiveness.

R-22 Refrigerant

R-22 is a single component HCFC refrigerant with low ozone depletion potential. It has long been used in a variety of air-conditioning and refrigeration applications in a variety of markets. Production of R-22 will cease in 2015 per the Montreal Protocol. Also commonly known as Freon.

R-410A Refrigerant
R-410A is classified as an HFC refrigerant and has no undesirable ozone depleting properties because it does not contain any chlorine. The operating pressures of R-410A are approximately 50% to 70% higher than that of R-22. R-410A systems use synthetic polyol ester (POE) oil. Unfortunately, POE oils are hydroscopic, meaning they readily absorb water. This can degrade the oil, causing harm to the entire system. R-410A systems should not be left open to the atmosphere longer than absolutely necessary.

Reciprocating Compressor
A type of compressor used in air conditioners that compresses refrigerant by using a type of "piston" action.

Refrigerant Lines

Set of two copper lines connecting the outdoor unit and the indoor unit.

Return Air

Air drawn into a heating/cooling unit after having been circulated from the cooling/heting unit output supply to a room.

Return Air Box

This is the sheet metal box that mounts directly to the return air grill. This allows the mating of the return duct to the grill.

Return Duct

The central heating or cooling system contains a blower that gets its air supply through this duct. The air from a room will move towards the lower pressure of the return duct. The duct also contains the properties of sound attenuation and is insulated.

Reversing Valve

A device in a heat pump that reverses the flow of refrigerant as the system switches from cooling to heating.

SEER
The Seasonal Energy Efficiency Ratio is a measure of the cooling efficiency of your air conditioner or heat pump. The higher the SEER number, the more efficient the system is at converting electricity into cooling power.

Sensible Heat

Heat energy that raises or lowers the temperature of a gas, liquid or solid when added or removed from that material.

Setpoint

The temperature at which a thermostat is set for desired comfort level.

SHGF

Solar Heat Gain Factor

Small Duct High Velocity

Designed for, and produces, at least 1.2 inches of external static pressure when operated at the certified air volume rate of 220-350 CFM per rated ton of cooling. The system uses high velocity room outlets generally greater than 1000 fpm which have less than 6.0 square inches of free area.

Sound Attenuators

Short lengths of flexible, baffled tubing. These tubes greatly reduce the audible sounds produced in the air movement process.

Split System
Refers to an air conditioner or heat pump that has components in two locations. Usually, one part of the system is located inside (evaporator coil) and the other is located outside your home (condenser coil).

Sub Cooling

Cooling of a liquid, at a constant pressure, below the point at which it was condensed.

Suction Line

Tube or pipe used to carry refrigerant gas from evaporator to compressor.

A temperature sensitive switch for controlling the operation of cooling and heating.

Thermostatic Expansion Valve

An automatic valve that feeds refrigerant to the evaporator coil. The amount of refrigerant fed to the coil is based on the line temperature leaving the coil. This is the preferred method to feed refrigerant to the coil as it is more accurate than an orifice or flo-rator commonly used. This is commonly call the TXV.

Ton

A unit of measure for cooling capacity. One ton = 12,000 BTUs per hour.

Under Sizing

Is the practice of selecting an air conditioner with a cooling capacity smaller than the cooling load.

Vacuum Pump

A pump used to remove air and moisture from a refrigeration system at a pressure below atmospheric pressure. This procedure is done prior to charging the system and assures that the system is free from all non-condensibles.

Vapor

The gaseous state of a substance.

Velocity

The speed at which a substance passes a point.

VOC

Volatile Organic Content

Water Manometer

Device used to measure pressure in inches of water.

Wet Bulb Temperature

Temperature read with a thermometer whose bulb is encased in a wetted wick.

Zoning

The practice of dividing a home into small sections for heating and cooling control. Each section is selected so that one thermostat can be used to determine its requirements.